Carbonate Sediments and Carbonate Rocks Flashcards
(113 cards)
1
Q
Difference between Siliciclastic and Terrigenous
A
- Siliciclastic is dominated by silicic fragments
- Terrigenous is made up of detrital material eroded under non-marine conditions from pre-existing rocks terranes
2
Q
Intraclast
vs
Lithoclast
A
- Intraclast - intrabasinal origin
- Lithoclast - Extrabasinal origin
3
Q
Spar vs Micrite
A
- Spar - can be calcite or aragonite. Coarser then micrite > 4 micrometers carbonate cement. Origing 1) preciptiation out of water as cemet. 2) recrystallization of micrite or othe carbonate grain
- Micrite- Cryptocrystalline carbonate mud. Origin is polygenic <4micrometers
4
Q
Allochems
A
Broken off parts of organisms. the most commun source of carbonate clasts in the marine environment is biological. Many marine invertebrates and certain very commun algae produce precipitated carbonate structures (shells, plates,etc..). Upon death of the organism, these grains (or Allochems) become part of the fabric of the carbonate rocks.
5
Q
Orthochem
A
The term used in the Folk classification to describe the micrite matrix and sparry calcite (sparite) cement in limestones.
6
Q
Allochem Wiki def.
A
Allochem is a term introduced by Folk[1] to describe the recognisable ‘grains’ in carbonate rocks. Any fragment from around ½mm upwards in size may be considered an allochem. Examples would include ooids, peloids, oncolites,pellets, fossil or pre-existing carbonate fragments.
7
Q
How ooids are formed?
A
Ooids form in areas where marine currents (for exemple, tidal currents) keep grains in motion.
8
Q
Hermatypic
A
Hermatypic corals are those corals in the order Scleractinia which build reefs by depositing hard calcareous material for their skeletons, forming the stony framework of the reef.
9
Q
what type of relationship hermatypic corals have with yellow-brown algae?
A
Algae provide nutrition (O2, glucose, amino acids)
Corals provide living space and easte nutrients (which used by algae) CO2, NO-3, NH+4 …
10
Q
What is the major importance of corals in the ecosystem?
A
- It creates new environments, so sedimentary structures are going to be different as well.
- It changes the destribution of light and energy of the environment
11
Q
which organisms play a important role on the biomineralization of calcium carbonate?
A
Foraminifera, Bryozons, Molluscs, Echinoderms, Corals, pteropods, coccolitophores
12
Q
which 2 organisms are the most important on the biomineralization of calcium carbonate?
A
Foraminifera and Coccolithopores
13
Q
Carbonates belong to a group of rocks formed by……… and/or………….reactions
A
…..precipitation….biochemical…
14
Q
Carbonates belong to a group of rocks formed by precipitation. Which other rocks are also included in the cabonates group?
A
- Evaporite (salt, gypsum, etc..)
- Chert (ilica) which also precipitates
- Carbonaceous rocks (coal)
- Others (phosphorites, iron-rich rocks)
15
Q
What controls the inorganic preciptation of calcite in water?
A
cpH controls calcite precipitation via the amount of CO2 disolved in water.
DEGASSING (Release of CO2)
- Increase in temperature (high temperature)
- Decrease in pressure (think of a coke open)
- Agitation
Note: you want shallow, warm and agitated (waves) environment.
16
Q
What type of environmet facilitates precipitation of Calcite?
A
A shallow, warm and agitated (waves) environment.
Coastal marine
17
Q
The chance of calcite being just CaCO3 is very ………..
They can also be made with ………….. and……………
A
Low
Mg and Fe
18
Q
……………is very important when talking about carbonates.
A
Biology
19
Q
Calcite vs Aragonite structure
A
Calcite is rhomboheadral
Aragonite is orthorhombic
20
Q
In termes of crystal structure and chemical composition, aragonite is a …………………… of calcite.
A
Polymorphic
21
Q
what happens with calcite in an acidic environment?
A
It dissolves
22
Q
Name it:
1- CaCO3
2- FeCO3
3- MgCO3
4- CaMg(CO3)2
A
1- calcite / aragonite
2-siderite
3-magnesite
4- dolomite
23
Q
How can you minimize the presence of carbonic acid in a aqueous environment?
A
Degassing:
- Increase temperature
- Decrease pressure
- Agitation
24
Q
……………….reactions are responsable for the majorite of carbonate precipitation in an equaeous environment
A
BIOGENIC
25
The majority of carbonates precipitation is .................
Biogenic
26
Organic carbonate deposition is dictated by whatever makes the............. of those carbonate secreating organisms to ...............
Biology/ succeed
27
What kind/s of biogenic processes are responsable for most carbonates precipitation?
- Direct precipitation
- Removal of CO2 linked to photosynthesis
- Bacterially mediated
Bacterially mediated (biologically induced/controlled and linked to physiological processes)
28
The distribution of carbonate-secreating algae is governed by......(6- T,S,L.a,C.s,Sub,F.a)....
- Temperature
- salinity
- light availability (depth)
- Current strength
- Substrate
- Food availability
29
Carbonate precipitation: The key controls are factors that limit/enhance the distribution/growth of particular organisms.The controls are:
- Temperature
- Salinity
- Light availability (depth)
- Current strength
- Substrate
- Food availability
30
What are the major controls on calcite precipitation?
- Inorganic reaction
- Biogenic
- Hermatypic corals(reef building)
- Water depth (CCD)
- Evolution and distribution of organisms
31
What is our current mode of carbonate sedimentation in the oceans?
Arogonitic + High-Mg calcite
32
Hard CaCO3 skeletons are secreted by........................corals, which live in .................... with yellow -brown ............
Hermatypic/ symbiosis/ algae
33
How the symbiotic relationship of corals and yellow-brown algae works?
The algae provides nutition and the corals provide living space and waste nutients (which are used by algae)
34
The algae provides .............. and the corals provide................ and ....................... (which are used by algae)
nutition/ living space/waste nutients
35
what are the major two impacts corals have in the environment?
They change/alter the distribution of light and energy in the environment
36
Corals create new.....................,so we can expect ....................to be also different.
environments/ sedimentary structures or deposition
37
CCD
Calcite compensation depth (CCD) is the depth in the oceans below which the rate of supply of calcite (calcium carbonate) lags behind the rate of solvation, such that no calcite is preserved.
or **Calcite dissolves at much higher rates than it can precipitates**
38
CCD: Dissolution of...................(first) then ................ increases with ......................and ...................
Aragonite/Calcite
Depth/temperature
39
Below CCD ,...................starts dissolving, but not.....................
Carbonates/ silicates
40
below CCD you can find ................rich sediments.
Silica
41
During green house Earth, the CCD will be ....................then todays compasation depth (4kms) . During icehouse Earth, the CCD will be .............then today depth. If we freeze Earth, then the CCD will be............... than todays depth.
**Lower** (increase temp - increase pH)/ **Same** (we are living in a icehouse earth)/ **higher** (Decrease temp is related to lower pH)
42
The greater the depth, the more. concentration of............, the more............ acid, the lower the..................
CO2/ Carbonic acid/ pH
43
Can you find calcareous organisms in the bottom of the ocean (greatre than 4kms)?
No, this is below the carbonate compensation zone. the calcite available would dissolve leaving just Silicious ooze (forms chert).
44
what is responsable for the great majority of silicious ooze in the bootom of the oceans (abyssal or greater than 4km)?
Wind-blown dust. (remember the sahara blowing silicious particle in the oceans)
45
...............ooze forms carbonate mudstone and ...................ooze forms chert.
Calcareous/ siliceous
46
Coral reefs have .........structures.
3D
47
What are the consequences of coral reefs to the newly modifyed environment which they have created?
- Incease in temperature of protected waters
- Decrease in energy (buffle currents)
- increase in salinity (depending on water cycle in protected lagoons)
- Increase in nutrients
- Increase in biomass
48
What type of oceans/seas do we form during the cenozoic period?
(present) Aragonitic seas
49
Global variations in ree-building/sediment-producing organisms during the phanerozoic is partly a functions of the composition of the sea water, resulting in.........seas, typified ............., and ...........sea typified by..................
these variations depend on ................ratio
calcitic/calcite
aragonitic/aragonite
Mg/Ca
50
Aragonite is ...................stable than calcite and at temperature of around 380 and 470C, ...................will turn into.............
**Less/ aragonite/calcite**
Calcite is a carbonate mineral and the most stable polymorph of calcium carbonate (CaCO3). The other polymorphs are the minerals aragonite and vaterite. Aragonite will change to calcite at 380–470 °C,[5] and vaterite is even less stable.
51
Wit increase in...............available in oceans, calcite will shift to................
Mg/ aragonite
52
During diagenisis, ...................will shift to .................
aragonite/ calcite
53
What happens in the water-ocean composition/ Mg/Ca ratio during green house earth?
levels of Mg decrease due to incorporation of Mg into the crust due to volcanism.
54
What happens in the water-ocean composition/ Mg/Ca ratio during icehouse earth?
With decrease volcanic activity, Mg level rise in oceans due to weathering.
55
Aragonite is more stable than calcite in the presence of?
Magnesium
56
with the increase of ................in the system, calcite shifts to aragonite
Magnesium
57
what happens to Magnesium during rapid sea-floor spreading?
Mg2+ in water, replaces Ca2+ in basalts to form Mg-rich clays, which in turn, **decreases Mg/Ca ratio** in oceans
58
During intense volcanic activity, oceans waters cicles through the crust (hight temperature basalt-seawater rxn) involve large-scale removal of.................content in the oceans allowing..............seas to exist. When sea-floor preading slows down, increase in Mg content due to....................
Mg/ Calcitic/ weathering
59
During greeanhouse climates, formation of LMC is favared over................
aragonite
60
During greenhouse climates, formation of ........... is favared over aragonite and reverse is true for icehouse climates.
LMC (low-Mg Calcite)
61
During icehouse climates, formation of aragonite + HMC is favared over............
LMC
62
Calcitic seas were coincident with times of rapid ..................................
sea-floor spreading
63
In general, precipitation of aragonite in preference to calcite is favored by ............ Mg/Ca ratio because of the inhibiting effect of Mg on calcite precipitation
High
64
Carbonate distribution is largelly controlled by:
- Cl.....
- Tec...
- Oce...
Climate
Tectonics
Oceongraphy (Controls the overall chemistry in the ocean)
65
Climate, Tectonics and Oceongraphy determine?
T/ S/ N/ T / S and T currents/ W.......activity
Temperature
Salinity
Nutitients distribution
Turbidity
Storm and tidal current intensity
Wave activity
66
What environment favors the highest rates of organic produtivity?
Shallow, warm and tropical climates (around 30 degrees from the equator)
67
What is an exanple of reforming corals?
Mostly light- dependent **Hermatypic corals** and calcareous geen algae.
68
Mostly light-dependent ...................corals and calcareous..............algae.
Whw\ere temperature drops below 15C to 0C, carbonate producers tend to be ...................... (e.g., .............foraminifera, calcareous red algae, bryozoa)
Hermatypic/ green
Light-independent / Bentic
69
Vast _majority_ of carbonates are formed in ......................waters
**warm.**
it doen't mean they don't form in cold waters
70
Where is life most abundant, at what zone?
Photic Zone!
71
At what depth (m), carbonate prdutivity (carbonate factory) is at maximum?
10-20 meters is the light saturation zone. below that, until ~ 100-200m is the base of photic zone
72
what are the 3 main components of carbonate sediments and limestones?
Grains, matrix and cement.
73
Give an example of skeletal grains
carbonate-producing animals, plants and bacteria
74
Give an example of non-skeletal grain
Peloids, coated grains, lithoclasts
75
Variours forms of......................is precipitaded during diagenesis, from very early to deep burial to exposure (eo-, meso-, and telogenesis)
Cement
76
Calcite cement likes to form around.............
calcite but it also forms around any grain. different than silica.
77
Diffrence between Brachiopos and bivalves?
!!!
In Bachiopods, each of the two valves displays bilateral symmetry and Bivalves have two symetrical valves.
78
Gastropods are very commun in...............marine environments. is mm-to-cm-sized coiled shapes, mostly b.........
Shallow/ Benthic
79
Cephalopods: Chambered shells (e.g. Nautiloids, ammonides). Ammonides are considerate great ...................
Index fossils
80
Converging evolution
2 different organisms evolved very differently by solving the same problem
81
3 types of molluscs
**Bivalves**: present in most aquatic environments (relatively simple, smoth shells)
**Gastropods**: very commun in shallow marine environments (mm- to cm-sized coiled shapes, mostly benthic)
**Cephalopods**: Chambered shells (e.g. Nautiloids, ammonites [great index fossil])
82
Brachiopods: mostly benthic, means..............., shallow marine.
more decorated shells than molluscs
Composed of multiple layers of LMC (early forms are phosphatic)
Lives in the ocean floor
83
Foraminifera: small (tens of microns to cm-scale), single-cell................or..............organisms.
Shell composed of HMC or LMC.
Very diagnostic! Good............and .......indicators.
Benthic or planktonic.
pH and salinity
84
Echinoderms:
Includes **.............** (sea urchins) and **............**(sea lilies) with skeletons composed or microporous plates and discs of LMC crystals.
They are **very diagnostic** and **good biomarkers**
**echinoids/ crinoids**
85
Corals: main components of modern reefs together w/ ...................
Modern forms are aragonite but calcite in the past.
Why is it aragonite nowadays?
Calcareous algae
High concentrations o aragonite + High-Mg calcite in the oceans.
86
Stromatoporoids: extinct, primarily calcitic (?)
Important...................... of the past
Mounded, laminated and dentritic (branch-like) forms
They have porous where they used to live
Very diagnostic!
Reef-.builder
because they are extinct, they may have formed as aragonite but since aragonite shifts to calcite it becames a gray area.
87
Diffence between Stromatoporoids and Stromatolites
!!!!
Stromatoporoids were animals and Stromatollites are bacteria.
88
Bryozoa: (Not corals or sponges) Fan shaped, dendritic and encrusting colonies of ..................animals. They live in structures for............and..............
mm to 1/2 meter in size
composed of aragonite or LMC
Well-adapted to deep, .................(20-30 degrees from the equator), marine setting.
Calcareous/ shelter and protection
Temperate
89
...................are very good in mixing (CO2 and temperature) what is going on in the atmosphere and the ocean.
The temperature of the surfice get transfered to the water, which changes its energy. Takes a lot longer for this to effect deep waters.
Ocean currents
90
Algae : (NOT an animal, NOT a plant)
Highly varied group of......................capable of secreating..............or......... around (even"within") their body.
Marine, brackish and freshwater groups.
Calcified stems and branches of......................, encrusting and delicately branching red..........are both BENTHIC.
Bits and pieces when compacted in the sediment record
Green and red algae are the same.
photosynthesizers/ calcite or aragonite
green algae/ algae
91
# Define Index fossils
!!!
Widely distributes
Narrow range in time
regarded as characteristic of a given geological formation
92
Not all algae are calcareoues.
true/false
true
93
Is sea-weed a plant?
No
94
Algae: Coccolithophores- yellow-green algae.
Presently widespread (white cliffs of dover), marine............composed of very small crystals (0.25-1 um) forming disk shaped coccoliths (2-20 um) which assemble into coccospheres (10-100 um).
Principal constituint of ................
They are great ...........fossils
!!!
plankton
Chalk
Index
95
Cyanobacterial structures and Grains
Stromatolites: are................and photosyntetic!!!
Filamentous, sticky, slimy surfaces of bacteria.
trap and stabilize fine-grained carbonate sediment, forming...........................
Grow into sheet-like, columnar and domal-structures
They live in very..............waters and
They form O2 as a waste product of photosyntesis.
Bacterial (bacterial "slime")
Microbial mats!!!!
Saline/ photic zone
("they used to dominate the planet")
96
Stramatolites Grow into sheet-like, columnar and domal-structures
As they died, due to sedimentation on top of them, they grow.........................with sediment.
They live in very..............environments, warm and.........................waters
They form O2 as a waste product of photosyntesis.
Interlayed
Saline/ shallow/ Photic (light saturation zone)
97
STROMATOLITES:
They form connected fillaments. They are one of the.................forms of life in the planet. One billion years before life appearded!
Responsable for life on the planet. Due to photosyntesis, they go rid of O2 as a waste produt.
Oldest
98
Cyanobacterial structures and grains:
ONCOIS:
............................structures
Form irregular, ~concentric layerss around a nucleus to form mm-to-cm-scale grains (around 1 1/2 cm across)
Bacterially-mediated
99
Non-skeletal grains:
ooids:
Spherical/ovoid carbonate grains composed of a nucleous surrounded by concentric, smooth layers of even thickness (type of coated grain)
Form in........../...........waters.
Saline/hypersaline
100
What are the requirements to form ooids?
What environment can you expect to find them?
* Bottom agitation (at least periodically) - gently agitated
* Shallow waters
* water supersaturated with respect to calcite or aragonite (implies warm temperatures (gets rid of CO2-increase pH)!!!)
* Limited amount of grain degradation (gently agitated).
Tidal flat.
101
Ooids are formed in very specific waters.
What evironment and conditions at which they are formed?
TIDAL FLAT
very shallow
warm
High pH
gently agitated - regurlaly (oscillating currents)
102
Carbonates like...................waters?
Alkaline
103
We can facilitate formation of ooids by minimizing.....................and..............pH of the water.
Carbonic acid/ increasing
104
Non-skeletal grains: peloids (pellets of some sort)
Relativelly small (\<200um), poligenetic grains composed of micro-or...............-crystaline carbonate.
May orginate as:
...........pallets. Desintegration of ..................algae
micritized grains via biochemical...............(acid environment) and bacterial growth. Reworking of lithic clasts of.....................
crypto
fecal
calcareous
dissolution
carbonate mud
105
Non-skeletal grains: peloids (pellets of some sort)
What is polygenic grains?
Formed in a varied of different ways.
106
Non-skeletal grains: peloids (pellets of some sort)
What is the main difference between peloids ad ooids?
Peloids have no internal structure and ooids have structured concentric layers
107
what is micitazation?
It forms..................
Is the break down of carbonaceous clasts through Chemical , Physical and biological processes.
Carbonaceous mud.
108
During micritization, grains are .....................away and boken down into.......................
Grains loose their ....................structure
dissolved/ micrite
internal
109
Non-skeletal grains: Lithoclasts
Intraclas: lithified/ partialy lithified carbonate fragment eroded from a nearby aproximately conteporaneoussediment.
Extraclast: fragment of carbonate/ non-carbonate rock derived from erosion of a unit located outside the depositional basin in which it is found. They are considerate....................
Carbonates don't usually travel...............
They weather very ease.
very rare
too far
110
Micrite:......................calcite
Formed as:
Lithified, mechanically deposited lime mud, or fine grained calcite crystals and particles formed in-place.
......................,\<=4 um, forming lime mud, lime ooze (very tiny in low energy environments), lime mudstone...
Microcrystalline
Cryptocristalline = microcrystalline
111
Micrite: microcrystalline calcite
Modes of formation:
Inorganic physico-chemical precipitation (rare?)
Precipitation linked to ..........or .........life processes (biological)
Disentregation of calcareous fossils and fine erosional debris from lithified.....................
algal or microbial
carbonates
112
Micite:
Two major sources are..............and................
Biological and Physical
113
Oncoids: Layered structures formed by.............................growth.
Clacium carbonate structures are deposite by encrusting .......................
Oncolides: Composed of oncoids. They are good indicators of ........................waters in ........................zone, but also known in fresh water environments. They rarelly exceed 10 cm in diameter.
Cyanobacterial
Microbes (microbial micrite!!)
Warm waters
